Resin coating method and apparatus

ABSTRACT

A resin coating method for applying resin to a predetermined region of a wiring board includes the steps of imaging an external appearance of the resin extruded from a resin application device; and automatically adjusting an amount of the resin extruded from the resin application device based on the external appearance of the resin obtained in the imaging step.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a resin coating method andapparatus for applying resin to a predetermined region of a printedwiring board.

[0003] 2. Description of Related Art

[0004] Conventionally, the production of semiconductor devices, in whichsemiconductor elements are mounted on a printed wiring board, involvesthe insertion of an insulating resin between the printed wiring boardpad and the semiconductor bump and, further, the use of insulating resinin regions of the printed wiring board that include leads. Thisso-called underfill is intended to protect the circuit surface and tostrengthen the bond between the semiconductor and the printed wiringboard.

[0005] Generally, there are two main methods of applying the insulatingresin (hereinafter simply resin): Injecting the resin between theprinted wiring board and the semiconductor elements after thesemiconductor elements have been mounted on the printed wiring board,and mounting the semiconductor elements on a printed wiring board thathas already been coated with resin.

[0006] Of the two methods of application, the latter is further dividedinto exposure and stamp methods.

[0007] The exposure method involves spraying drops of resin from anozzle that is moved over the surface of the printed wiring board,covering a predetermined region with a coating having a thickness, forexample, of approximately 50-100·m.

[0008] By contrast, the stamp method involves dropping a predeterminedamount of resin from a nozzle onto a central portion of the printedwiring board and then using the force with which the semiconductorelements are mounted on the printed wiring board to spread the resinover a predetermined region with a coating having a thickness, forexample, of approximately 10-100·m.

[0009] The stamp method of application has come to be used with lessfrequency for large semiconductor elements with surface dimensions onthe order of millimeters, being optimally suited to smallersemiconductor elements having surface dimensions of 0.3 mm or less.

[0010] An example of the mounting of such smaller semiconductor elementson a printed wiring board is shown in FIG. 1, which shows a head sliderassembly for a hard disk drive. In this case, a head IC chip 1 ismounted on a printed wiring board suspension 2.

[0011] In such a case, the resin application device is usually adispenser (not shown in the diagram) having a syringe filled with resin,the dispenser being able to raise and lower the syringe.

[0012] In order to apply the resin, a nozzle on a lower part of thesyringe is positioned at a predetermined height above a surface of thesuspension 2 and a predetermined amount of resin 3 is extruded from thesyringe by compressed air. The extruded resin 3 is substantiallyspherical in shape, and contacts and adheres to the suspension 2. Whenthe syringe is lifted the resin 3 separates from the syringe and spreadsacross a predetermined position on the surface of the suspension 2.Thereafter a head IC chip 1 is positioned above and pressed onto thesuspension, thus further spreading the resin 3 as well as adhering andfixedly mounting the head IC chip 1 onto the suspension 2.

[0013] More specifically, as can be seen in FIG. 1, a wiring pattern 4may be formed on a top surface of the suspension 2 and a gold pad 5 maybe formed at an edge portion of the wiring pattern 5. At the same time,a gold bump 6 may be formed on a bottom surface of the head IC chip 1.The gold pad 5 and the gold bump 6 are coupled and a predeterminedregion between the head IC chip 1 and the suspension 2 including thegold pad 5 and the gold bump 6 is covered with the resin 3.

[0014] A plurality of suspensions 2 may for example be set atop a stageat a resin application device and the suspensions 2 subjected to theabove-described coating process. In this case, in order to resin-coat apredetermined product lot with a predetermined amount of resin, theresin application device is set to specific conditions at the start ofcoating. When after repeated coating the resin is used up, a new syringeis installed.

[0015] In the above-described case, the head IC chip 1 is, for example,just 1×1 mm, and so the amount of resin used in the coating is, forexample, approximately 0.05 mg. Such small amounts over such smallsurfaces requires precision in the application of the resin 3.

[0016] However, because the amount of resin 3 involved in individualapplications is small, it can happen that slight changes in ambientconditions during application, such as, for example, slight changes intemperature, causes slight changes in the amount of resin 3 applied,despite the resin application device being set to predeterminedconditions beforehand.

[0017] Conventionally, in order to maintain the amount of resin 3 to beapplied at the predetermined volume, a visual inspection is made of theamount of resin, if any, protruding from the edges of the semiconductorelements in a state in which the printed wiring board has been coatedand the semiconductor elements mounted thereon in order to determine iftoo much resin or too little resin is being applied, after which theresin amount is adjusted as necessary. Additionally, visual inspectionof the resin drop just before it separates from the nozzle or theexternal appearance of the resin 3 coating the stage are also used todetermine the presence of change in the amount of resin applied.

[0018] However, the very small amounts of resin involved make itdifficult to discern changes in that amount by the conventional methods.In addition, adjustment of the amount is often left to the discretion ofan operator, which means it is often done manually and at arbitrarytimes. Such methods of adjustment are unsuited to cases in which theamount of resin applied changes continuously due to a variety ofenvironmental and other factors.

BRIEF SUMMARY OF THE INVENTION

[0019] Accordingly, it is an object of the present invention to providean improved and useful resin coating method and apparatus in which theabove-described disadvantage is eliminated.

[0020] The above-described object of the present invention is achievedby a resin coating method for applying resin to a predetermined regionof a printed wiring board comprising the steps of:

[0021] imaging an external appearance of the resin extruded from a resinapplication device; and

[0022] automatically adjusting an amount of the resin extruded from theresin application device based on the external appearance of the resinobtained in the imaging step.

[0023] The above-described object of the present invention is alsoachieved by a resin coating apparatus for applying resin to apredetermined region of a printed wiring board, comprising:

[0024] an imaging unit for imaging an external appearance of the resinextruded from the resin coating apparatus; and

[0025] an automatic adjustment unit for automatically adjusting anamount of the resin extruded from the resin coating apparatus based onthe external appearance of the resin obtained in the imaging step.

[0026] According to the above-described aspects of the presentinvention, the amount of resin expelled, in other words, the amount ofresin to be used to coat the printed wiring board, is set according tothe dimensions of the semiconductor elements mounted on the printedwiring board. The present invention is most effective with semiconductorelements measuring not more than 0.3 mm a side, though it is not limitedto use with semiconductor elements of such dimensions.

[0027] A preferred method for automatically adjusting the amount ofresin extruded from the resin coating apparatus is one in which adifference between a preset coating amount and an actual coating amountas determined by the external appearance of the resin is sensed and thisdifference used as feedback to adjust the amount of resin extruded. Inthis case, it is preferable that relational data relating the externalappearance of the resin and the coating amount be stored as a referencetable in the resin coating apparatus. An ordinary camera can suffice foruse as the imaging device. As a method of adjusting the amount of resinextruded, it is preferable to regulate either the pressure of compressedair used to expel the resin, and/or the amount of time during which thatflow of air continues. For accuracy and ease of control, regulating thetiming of the air flow is preferable.

[0028] It should be noted that the foregoing can be applied to any orall of the embodiments to be described later.

[0029] It will be appreciated by those of skill in the art that thefactors that directly affect the amount of resin extruded from thesyringe and cause it to vary from a predetermined desired amount includebut are not limited to changes in air pressure, changes in temperature,and changes in the viscosity of the resin due to changes in thecomponents of the resin over time.

[0030] However, according to the above-described aspects of the presentinvention, the amount of resin extruded can be quickly and accuratelyadjusted as necessary.

[0031] ADDITIONALLY, THE ABOVE-DESCRIBED OBJECT OF THE PRESENT INVENTIONIS ALSO ACHIEVED BY A RESIN COATING METHOD FOR APPLYING RESIN TO APREDETERMINED REGION OF A PRINTED WIRING BOARD, COMPRISING THE STEPS OF:

[0032] MEASURING A TEMPERATURE OF AN EXTRUSION NOZZLE OF A RESINAPPLICATION DEVICE; AND

[0033] automatically adjusting an amount of the resin extruded from theresin application device based on the temperature of the nozzle.

[0034] According to this aspect of the invention, an appropriatetemperature sensor can be used to measure the temperature of theextrusion nozzle, and the method of adjustment may be either manual orautomatic.

[0035] Additionally, adjustments in the amount of resin extrudednecessitated by changes in the amount of resin extruded from theextrusion nozzle due to a change in the viscosity of the resin caused bya change in the temperature of the nozzle can be performed relativelyeasily, on the basis of the temperature data. Additionally, if in thiscase the amount of resin extruded is adjusted automatically, then theamount of resin extruded can be quickly and accurately adjusted asnecessary.

[0036] Additionally, the above-described object of the present inventionis also achieved by a resin coating method for applying a resin to apredetermined region of a printed wiring board comprising positioning anextrusion nozzle of a resin application device at a predeterminedreference height.

[0037] The reference height is not particularly limited. However, interms of eliminating with certainty those elements that cause the amountof resin extruded to vary, controlling the height of the nozzle withrespect to the printed wiring board on which the resin coating is to beapplied is desirable. In this case, for example, a glass plate may beplaced at a height identical to a height at which the printed wiringboard is positioned, with an upper surface of the glass plate serving asa reference surface. The extrusion nozzle from which resin is extrudedmay then be contacted against the reference surface so as to adjust thenozzle to a reference height. The contact may be detected by a varietyof suitable methods, including use of a magnetorestrictor to detect thepresence of an electric current when pressure is applied or by using alight-emitting element and a light-receiving element to detect when thelight is cut off. By programming the resin application device to raiseand lower the syringe (or resin extrusion nozzle, as the case may be)according to a set schedule, the reference height contained in thatprogram can be replaced with a newly obtained reference height.

[0038] According to the above-described aspect of the invention, theextrusion nozzle is positioned at a predetermined height when mounted onthe resin application device, so the distance between the extrusionnozzle and the printed wiring board does not change even when, forexample, the syringe containing the resin becomes empty and is replacedwith a new syringe in an operation that can cause the height at whichthe extrusion nozzle is positioned to vary.

[0039] As a result, in the present invention the distance between thenozzle and the printed wiring board is set to a predetermined value andhence the volume of resin extruded does not change, hence avoiding asituation in which the height of the nozzle changes, and accordingly,the distance between the tip of the nozzle and the printed wiring boardchanges, such that when that distance exceeds a predetermined value theamount of resin extruded also exceeds a predetermined amount, andconversely, when that distance falls below a predetermined value theamount of resin extruded also decreases below a predetermined amount.

[0040] The above-described object of the present invention is alsoachieved by a resin coating method for applying resin to a predeterminedregion of a printed wiring board, comprising the steps of:

[0041] IMAGING AN EXTERNAL APPEARANCE OF A RESIN DROP AFTER THE RESINDROP HAS BEEN EXTRUDED FROM A NOZZLE OF A RESIN APPLICATION DEVICE BUTBEFORE THE RESIN DROP CONTACTS THE PRINTED WIRING BOARD; AND

[0042] adjusting a distance between a tip of the nozzle and the printedwiring board based on the external appearance of the resin drop obtainedin the imaging step.

[0043] If for some reason the distance between the nozzle and theprinted wiring board becomes too short, then when the nozzle is liftedafter coating the printed wiring board resin remains on the tip of thenozzle. If such a condition persists, then at some point during thecoating process the amount of residual resin remaining on the tip of thenozzle peels off therefrom, coating the printed wiring board with anabnormally large amount of resin.

[0044] However, according to the above-described aspect of the presentinvention, adhesion of excess resin to the tip of the nozzle can beprevented by, for example, substantially matching the distance betweenthe tip of the nozzle and the printed wiring board to a diameter of thedrops of resin. In this case, it would be even more desirable to compilea database relating resin drop diameter to optimal distance between thenozzle and the printed wiring board so as to automatically adjust thedistance to the diameter.

[0045] ADDITIONALLY, THE ABOVE-DESCRIBED OBJECT OF THE PRESENT INVENTIONIS ALSO ACHIEVED BY A RESIN COATING METHOD FOR APPLYING RESIN TO APREDETERMINED REGION OF A PRINTED WIRING BOARD, COMPRISING THE STEPS OF:

[0046] IMAGING A RESIDUAL AMOUNT OF THE RESIN ON AN EXTRUSION NOZZLE OFA RESIN APPLICATION DEVICE FROM WHICH THE RESIN IS EXPELLED; AND

[0047] washing the nozzle when the residual amount exceeds apredetermined amount.

[0048] According to this aspect of the invention, by washing the nozzlebefore the coating amount varies from a desired amount, imperfections inthe coating can be avoided.

[0049] In this case, any of a variety of suitable methods for washingthe nozzle can be employed, including removing the residual resin by airblower, by wiper, by immersion in a washing solution or by melting theresidual resin off.

[0050] Other objects, features and advantages of the present inventionwill become more apparent from the following detailed description whenread in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0051]FIG. 1 is a diagram showing a conventional example of a smallsemiconductor element mounted atop a printed wiring board;

[0052]FIG. 2 is a flow chart of steps involved in production of asemiconductor device when mounting a semiconductor element on theprinted wiring board, including a resin coating step as per each of theembodiments of the present invention;

[0053]FIG. 3 is a schematic diagram of a resin coating apparatus used toperform a resin coating method according to the first embodiment of thepresent invention;

[0054]FIG. 4 is a flow chart showing steps in a resin coating methodaccording to the first embodiment of the present invention;

[0055]FIG. 5 is a schematic diagram of a resin coating apparatus used toperform a resin coating method according to a variation of the firstembodiment of the present invention;

[0056]FIG. 6 is a schematic diagram of a resin coating apparatus used toperform a resin coating method according to a second embodiment of thepresent invention; FIG. 7 is a flow chart showing steps in a resincoating method according to the second embodiment of the presentinvention;

[0057]FIG. 8 is a schematic diagram of a resin coating apparatus used toperform a resin coating method according to a third embodiment of thepresent invention;

[0058]FIG. 9 is a flow chart showing steps in a resin coating methodaccording to the third embodiment of the present invention;

[0059]FIGS. 10A and 10B are diagrams of a resin coating apparatus usedto perform a resin coating method according to a fourth embodiment ofthe present invention, in which FIG. 10A shows a state prior to coatingand FIG. 10B shows a state at time of coating;

[0060]FIG. 11 is a flow chart showing steps in a resin coating methodaccording to the fourth embodiment of the present invention;

[0061]FIG. 12 is a schematic diagram of a resin coating apparatus usedto perform a resin coating method according to a fifth embodiment of thepresent invention; and

[0062]FIG. 13 is a flow chart showing steps in a resin coating methodaccording to the fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0063] A description will now be given of embodiments of the presentinvention, with reference to the accompanying drawings. It should benoted that identical or corresponding elements in the embodiments aregiven identical or corresponding reference numbers in all drawings, withdetailed descriptions of such elements given once and thereafteromitted.

[0064] In order to facilitate an understanding of the invention, adescription will first be given of a process of manufacturing asemiconductor device using the conventional head slider assemblydescribed above.

[0065]FIG. 2 is a flow chart of steps involved in production of asemiconductor device when mounting a semiconductor element on theprinted wiring board, including a resin coating step as per each of theembodiments of the present invention.

[0066] Using a wire bonding device, a gold bump is formed on a bottomsurface of a head IC chip in a step S10.

[0067] At the same time, a gold pad is formed on a wiring pattern on atop surface of the suspension in a step S20. Next, a resin coating isapplied as an underfill in a center of a portion to be mounted on thehead IC chip on a side of the suspension on which the gold pad is formedin a step S30. Then, the suspension is fixedly mounted atop a stage withthe gold pad and resin coated part facing upward in a step S40.

[0068] The head IC chip is vacuum-attached to a bonding tool of abonding unit and transported to a location of the suspension, where thehead IC chip is aligned atop the suspension S50.

[0069] Lowering the bonding tool depresses the head IC chip, causing thegold bump to be pressed by the gold pad. At this time, the head IC chipspreads the resin. The resin spreads until it just protrudes from anouter periphery of the head IC chip (see FIG. 1). Additionally, at thesame time as the head IC chip is pressed, the periphery of the head ICchip is subjected to ultraviolet light, causing that part of the resinprotruding from the outer periphery of the head IC chip to partiallyharden in a step S60.

[0070] Next, the head IC chip is subjected to ultrasound vibration whileunder pressure so as to bond the gold bump and gold pad together in astep S70. It should be noted that the head IC chip continues to beexposed to ultraviolet light during this time.

[0071] Up to the present stage, except for that part of the resin thatprotrudes from the outer periphery of the head IC chip, the resindirectly beneath the head IC chip remains unhardened, and thus providesno impediment to the above-described bonding of the gold bump and goldpad.

[0072] Finally, the head IC chip to which the suspension has been bondedis moved to a furnace and heated so as to harden the remainingunhardened portion of the resin, thus forming the underfill andcompleting assembly of the head slider assembly in a step S80.

[0073] A description will now be given of a basic structure and functionof a resin coating apparatus used in executing the resin coating methodaccording to the present invention.

[0074]FIG. 3 is a schematic diagram of a resin coating apparatus used toperform a resin coating method according to the first embodiment of thepresent invention.

[0075] As shown in the diagram, the resin coating apparatus 10 compriseschiefly a dispenser 12 and a controller 14 that controls the movement ofthe dispenser 12.

[0076] The dispenser 12 includes a syringe 16, a retaining portion 18that grasps the syringe 16, and a supporting portion 20 that can raiseand lower the retaining portion 18.

[0077] The syringe 16 may for example be formed to a substantiallycylindrical shape using a plastic material, and is filled with apredetermined volume of a coating resin 22. An upper end of the syringe16 is sealed by a lid 16 a, with a nozzle 16 b formed at a lower end forthe purpose of extruding the resin 22 therefrom. One end of a compressedair line 24 is detachably attached to the lid 16 a. For descriptiveconvenience, a detailed description of the compressed air line 24 isdeferred until later. The syringe 16 is clamped by the retaining portion18. When the resin 22 has been used up and the syringe 16 becomes empty,the empty syringe 16 is removed from the retaining portion 18 andreplaced with a new syringe 16 filled to a predetermined volume with theresin 22. One end 18 a of the retaining portion 18 retains the syringe16 while the other end of the retaining portion 18 b is supported insuch a way as to ascend and descend along a shaft 26 of the supportingportion 20 to be described later.

[0078] The supporting portion 20 includes a base 28, the above-describedshaft 26 rising from the base 28, and a drive portion 30 that ascendsand descends.

[0079] The base 28 is driven by a drive source not shown in the diagram,such that, for example, the base 28 is mobile along a rail. The driveportion 30 is provided with a motor 34 having a gear 32, and is fixedlymounted at a predetermined position along the shaft 26 by a mountingportion 36. The other end 18 b of the retaining portion 18 iscylindrical in shape and mounted so as to be slidable along the shaft26, with a gear groove formed on an outer periphery of the end 18 b(though not shown in the diagram) engaging the gear 32 of the motor 34.As a result, when the motor 34 is activated and causes the gear 32 torotate, the retaining portion 18 is raised or lowered accordingly. Themovement of the motor 34 of the supporting portion 20 is controlled bythe controller 14 as described below.

[0080] The compressed air line 24 is connected, for example, to a 0.6 MPsource of pressurized air. A pressure adjustment valve 38 is provided onan upstream side of the compressed air line 24 and an electromagneticvalve 40 is provided on a downstream side. The pressure adjustment valve38 and the electromagnetic valve 40 together comprise one part of thecontroller 14.

[0081] In addition to the pressure adjustment valve 38 and theelectromagnetic valve 40, the controller 14 is also provided with acontrol instrument 42 that controls the movement of the motor 34 of thesupporting portion 20.

[0082] It should be noted that the resin coating apparatus 10 isprovided with a stage 44 capable of being moved by a motive source notshown in the diagram. A plurality of printed wiring boards 46 areprovided on the stage 44 (although only one is shown in FIG. 3), so thatby moving the stage 44 the printed wiring boards 46 are also moved, thuspermitting a plurality of printed wiring boards 46 to be coated withresin continuously.

[0083] A resin application process employing the resin coating apparatus10 having the structure described above, is performed according to thefollowing general order.

[0084] First, a plurality of printed wiring boards 46 are positionedatop the stage 44.

[0085] Second, a fresh syringe 16 filled with a predetermined volume ofresin 22 is installed at the retaining portion 18. The resin 22 may forexample by composed of an acryl component, with each syringe filledwith, for example, 5 ml of resin 22. With this one syringe 16, forexample, approximately 80,000 printed wiring boards 46 can be coatedwith resin 22.

[0086] Third, one end of the compressed air line 24 is connected to thelid 16 a of the syringe 16.

[0087] Fourth, the following coating operation is carried out based on aprogram installed in a CPU of the control instrument 42 of thecontroller 14.

[0088] The motor 34 is driven by a motor drive signal 48 from thecontrol instrument 42. The position to which the syringe 16, which isdriven by the motor 34, is raised or lowered is numerically controlled.The syringe 16, which is positioned at a predetermined height position,is then lowered until a tip of the nozzle 16 b attains a predetermineddistance from the printed wiring board, for example 150·m, at whichpoint lowering of the nozzle 16 b is halted.

[0089] The compressed air line 24 is controlled so as to operateaccording to the specifications of the printed wiring board 46 to beprocessed, in such a way that control signals 50, 52 from the controlinstrument 42 set the degree of opening of the pressure adjustment valve38 as well as the open-and-close cycles of the electromagnetic valve 40.For example, when the air pressure is reduced to approximately 0.5 Mpa,the electromagnetic valve 40 is kept open for 60 ms and then closed for1440 ms, in a cycle that repeats itself. As a result, a predeterminedvolume of resin 22 is extruded from the syringe 16 and coats the printedwiring board 46. The conditions under which air is sent to the syringe16, in other words, adjustment of the amount of resin extruded from thenozzle 16 b of the syringe 16 by compressed air, for example in a casein which the amount of the coating is increased, can involve eitherincreasing the extent of the opening of the pressure adjustment valve 38so as to raise the pressure of the air sent into the syringe, orchanging the cycle of the electromagnetic valve 40 to keep theelectromagnetic valve 40 open longer, or both. Of these two types ofadjustments, readjusting the cycle of the electromagnetic valve 40yields relatively more precise adjustment of the amount of resinextruded, in other words, is the easier of the two ways of adjusting theamount of resin 22 used.

[0090] The predetermined amount of resin 22 extruded from the nozzle 16b of the syringe 16 by compressed air temporarily assumes the shape of aball of resin 22, with a top part attached to the nozzle 16 b. A bottompart of the resin 22 thereafter contacts the printed wiring board 46 andattaches itself thereto. The syringe 16 is then raised, causing theresin 22 to separate from the nozzle 16 b and spread over the surface ofthe printed wiring board 46.

[0091] A description will now be given of a resin coating methodaccording to a first embodiment of the present invention, with referenceto the same FIG. 3.

[0092] In order to perform the resin coating method according to thefirst embodiment of the present invention, the resin coating apparatus10 described above additionally and further has a rotary plate (stage)56 driven by a motor 54, a camera (imaging means) 58 for taking aphotograph (i.e., an image) of the rotary plate 56; and a monitor 60 forlooking at (i.e., examining) the image obtained by the camera 58. Themonitor 60 is equipped with an image analyzer which produces digitizedinformation from each picture element of the image and which isprocessed by calculator 62 which sends a control signal 64 to thecontrol instrument 42.

[0093]FIG. 4 is a flow chart showing steps in a resin coating methodaccording to the first embodiment of the present invention.

[0094] As shown in FIG. 4, the resin coating method according to thefirst embodiment of the present invention involves an imaging step S106in which the external appearance of the resin 22 extruded from the resincoating apparatus 10 is photographed and a step S110 in which theapplication amount of resin 22 extruded from the resin coating apparatus10 is adjusted based on the external appearance obtained in the imagingstep S106, in other words, the coating amount is automatically adjusted.Further, in this case, prior to the imaging step S106 the resin 22 isstretched across the rotary plate 56 in a step S104, and the surfacearea of the resin 22 spread across the top of the rotary plate 56 afterthe imaging step Si 06 is measured in a step S108.

[0095] In other words, when for a variety of reasons it is deemednecessary to check for variation in the coating amount of the resin andto adjust the coating amount accordingly, the resin coating apparatus 10is moved and the syringe 16 positioned at the rotary plate 56 in a stepS100. Then the resin 22 is extruded under programmed actual coatingconditions onto the rotary plate 56 in a so-called dry run step S102.The dry run is carried out as appropriate whenever for any reason achange occurs in the amount of resin coating the printed wiring boardsduring a production line run. Additionally, the dry run may also becarried out on a regular and periodic basis for the purpose of checkingand adjusting the amount of resin used in the coating, for example a dryrun once every ten printed wiring board coatings.

[0096] During a dry run, depending on the state of rotation of therotary plate 56, centrifugal force causes the extruded resin 22 toelongate across the surface of the rotary plate 56 in the step S104. Thespread resin 22 develops into a thin disc-like shape. In this case, thethickness of the resin 22 remains virtually unchanged and uniform evenif there is a change in the amount of resin used in the coating.Accordingly, by noting changes in the surface area of the resin 22 it ispossible to note any changes in the coating amount of resin 22 as well.

[0097] As described above, the external appearance of the resin 22 isphotographed with the camera 58 in the step S106 and the resulting imageanalyzed in the step S108. The image so acquired is used to determinethe surface area of the resin 22 spread across the surface of the rotaryplate 56. Ordinarily, when the measurement object is irregular, it isnecessary to scan the entire image in order to obtain an approximationof its surface area. However, according to the present embodiment, thesurface area can be obtained using just the diameter of thesubstantially circular shape formed by the spreading resin 22, thusmaking image analysis easy and quick.

[0098] Based on the surface area data obtained as described above, acorrelation is found between surface area and coating amount byreferring to a table of such correlations. Any difference between thepredetermined programmed coating amount and the actual coating amount asobtained from the surface area data is sent to the control instrument42, and the control instrument 42 used to reset the open-and-close cycleof the electromagnetic valve 40 in order to reacquire, or re-establish,the correct, that is, the predetermined coating amount in a step S110.

[0099] More specifically, when for example the coating amount obtainedfrom the surface area data is less than the predetermined programmedcoating amount, in other words when the amount of resin extruded duringthe production line run is less than a predetermined coating amount,then the program is changed so that the amount of time during which theelectromagnetic valve 40 is open is lengthened to a degree correspondingto the amount of the shortfall in the coating volume, with applicationof the resin 22 thereafter carried out under the new coating conditions.

[0100] According to the resin coating method according to the firstembodiment of the present invention as described above, the amount ofresin 22 extruded from the resin coating apparatus 10 is automaticallyadjusted according to the external appearance of the resin, so there isno lag in taking corrective action. Additionally, change in the surfacearea of the resin, that is, change in the amount of resin 22 used incoating the printed wiring board 46, can be quantified and understoodaccurately, and the amount of resin 22 used in the coating adjustedprecisely.

[0101] A description will now be given of a variation of the resincoating method according to the first embodiment of the presentinvention.

[0102]FIG. 5 is a schematic diagram of a resin coating apparatus used toperform a resin coating method according to a variation of the firstembodiment of the present invention.

[0103] The basic structure of the resin coating apparatus 70 used toperform the variation of the resin coating method according to the firstembodiment of the present invention is essentially identical to theresin coating apparatus 10 used in the first embodiment, though withcertain additions to be described below.

[0104] The resin coating apparatus 70 is provided with one or more xenonlamps 72. In the case of the resin coating apparatus 72 shown in FIG. 5,there are two such xenon lamps 72. Additionally, a filter 74 that onlypasses fluorescent light 78 is either installed directly on the camera58 or provided separately from the camera 58 in a space between thecamera 58 and the rotary plate 56.

[0105] In the imaging step S106 described above, the resin coatingmethod according to the variation of the first embodiment projects lightof a predetermined wavelength onto the resin 22 so as to cause the resin22 to fluoresce, separates the generated fluorescent light from light ofother wavelengths, obtains a fluorescent image of the resin 22 and usesthe fluorescent image to measure the surface area of the resin 22.

[0106] That is, light of a predetermined wavelength is generated using axenon lamp or lamps 72 as a light source, thus projecting xenon light 76onto the resin 22 and the rotary plate 56. The rotary plate 56 is, forexample, a metallic plate, and so despite absorbing a portion of thexenon light 76 nevertheless reflects substantially all of the xenonlight 76. By contrast, the resin 22 reflects the xenon light 76 andgenerates fluorescent light 78 from the energy of the absorbed xenonlight 76.

[0107] Of the xenon light 76 and fluorescent light 78 that reaches thefilter 74, only the fluorescent light 78 passes through the filter 74and is captured by the camera 58. Thereafter the process of applying acoating of resin 22 onto the printed wiring board 46 is the same as forthe resin coating method according to the first embodiment of thepresent invention as described above.

[0108] In the event that the resin 22 has color, then there is no needfor special processing like that described for the variation of thefirst embodiment as above. If, however, the resin 22 is transparent,then exposure to sunlight will turn virtually every picture elementpertaining to the images of the resin 22 and the rotary plate 56substantially totally white, making the image difficult to identify.Nevertheless, according to the above-described variation of the firstembodiment of the present invention, even in the event that the resin 22is transparent the same effects and advantages as with the firstembodiment of the present invention can be obtained.

[0109] It should be noted that, in a case in which the lots of resin 22are mixed, that is, some are transparent and others colored, then,according to the above-described variation of the first embodiment ofthe resin coating method as described above, the same resin coatingapparatus 70 can still be used without interruption.

[0110] A description will now be given of a resin coating methodaccording to a second embodiment of the present invention.

[0111]FIG. 6 is a schematic diagram of a resin coating apparatus used toperform a resin coating method according to a second embodiment of thepresent invention. FIG. 7 is a flow chart showing steps in a resincoating method according to the second embodiment of the presentinvention.

[0112] The basic structure of a resin coating apparatus 80 used toperform the resin coating method according to the second embodiment ofthe present invention is essentially unchanged from that of the resincoating apparatuses 10, 70 described above. However, the apparatus 80does additionally comprise a temperature sensor 82 and a control unit84.

[0113] The temperature sensor 82, for example, may optimally be aradiation thermometer. The temperature sensor 82 is positioned so as tobe able to sense a surface temperature at the tip of the nozzle 16 b.Signals 83 of the temperature data detected by the temperature sensor 82are sent to the control unit 84. The control unit 84 is equipped with areference table for correcting the amount of resin 22 used in thecoating depending on the surface temperature of the tip of the nozzle 16b, specifically, in this case, as with the first embodiment,transmitting to the control instrument 14 a control signal that changesthe open-and-close cycle schedule of the electromagnetic valve 40 asappropriate.

[0114] As shown in FIG. 7, the resin coating method according to thesecond embodiment of the present invention comprises a step S200 inwhich the temperature of the nozzle 16 b of the resin coating apparatus80 is measured and a step S202 in which the amount of the coating isadjusted automatically on the basis of the temperature data obtained inthe nozzle temperature measurement step S200.

[0115] In other words, the temperature at the nozzle 16 b of the resincoating apparatus 80 is measured by the temperature sensor 82 atappropriate intervals. The control unit 84 then resets the cycle of theelectromagnetic valve 40 depending on the temperature measured, sendinga signal to that effect to the controller 14, changing the cycle of theelectromagnetic valve 40 and adjusting the amount of resin 22 extrudedfrom the resin coating apparatus 80. Coating thereafter continuessubject to the new conditions.

[0116] According to the resin coating method according to the secondembodiment of the present invention, changes in the temperature of thenozzle 16 b with repeated coating applications that in turn cause theviscosity of the resin 22 to change and the amount of resin 22 extrudedfrom the nozzle 16 b to vary are offset by sensing the temperature atthe nozzle 16 b and automatically adjusting the amount of resin 22extruded therefrom. Thus a relatively simple device and method sufficesto support accurate and timely corrective action with respect to theamount of resin 22 extruded from the resin coating apparatus 80.

[0117] A description will now be given of a resin coating methodaccording to a third embodiment of the present invention.

[0118]FIG. 8 is a schematic diagram of a resin coating apparatus used toperform a resin coating method according to the third embodiment of thepresent invention. FIG. 9 is a flow chart showing steps in a resincoating method according to the third embodiment of the presentinvention.

[0119] In order to perform the resin coating method according to thethird embodiment of the present invention, a resin coating apparatus 90is used that has essentially the same basic structure as the resincoating apparatuses described above but with the addition of a mechanismfor positioning the tip of the nozzle 16 b at a predetermined height.

[0120] The height-positioning mechanism further comprises a glass plate94 mounting a magnetorestrictor 92.

[0121] The glass plate 94 is positioned together with a wiring board 46at a height identical to a height of the wiring board 46 atop the stage44. In other words, the glass plate 94 serves as a reference surface(that is, a predetermined reference height) at time of coating. When thetip of the nozzle 16 b from which the resin 22 is extruded contacts theglass plate 94, that is, the magnetorestrictor 92, the pressing of themagnetorestrictor 92 generates an electric current. The controller 14receives a signal 93 of the current so generated and interrupts thedrive of the motor 34, resets the reference height set in the controller14 program with the new reference height data and generates a motordrive signal that raises the nozzle 16 b a predetermined amount.

[0122] A description will now be given of the resin coating methodaccording to the third embodiment of the present invention, withreference to FIG. 9.

[0123] When the syringe 16 becomes empty of resin 22, the syringe 16 isreplaced by a fresh syringe 16 from the dispenser 12 in a step S300.Next, the stage 44 is moved and the glass plate 94 placed directlybeneath the fresh syringe 16 in a step S302. The motor 34 is thenstarted and the syringe 16 is gradually lowered in a step S304. When thetip of the nozzle 16 b of the syringe 16 contacts the magnetorestrictor92 in a step S306 and the magnetorestrictor 92 is pressed andrestricted, an electric current is generated in the magnetorestrictor92. An electrical signal 93 based on the electric current so generatedis then transmitted to the controller 14. The controller 14 temporarilyinterrupts the drive of the motor 34, replaces the reference heightdata, and generates a motor drive signal that raises the nozzle 16 b bya predetermined amount. In so doing, the syringe 16 that is driven bythe motor 34 is raised to a predetermined height with respect to thenewly set reference height and maintained at that height position forsubsequent coating operations in a step S308.

[0124] According to the resin coating method according to the thirdembodiment of the present invention, when the height at which the tip ofthe nozzle 16 b is positioned changes, either because, for example, thesyringe 16 containing the resin 22 used for coating becomes empty and isreplaced with a new syringe 16 or for some other reason, the tip of thenozzle 16 b is maintained at a predetermined height with respect to areference surface when installed on the resin coating apparatus 90.Thereafter the syringe 16, which is positioned at a predetermined heightabove the reference surface, is then lowered a predetermined amount bythe control program. As a result, the distance between the tip of thenozzle 16 b and the printed wiring board 46 is maintained at apredetermined value even after the syringe has been replaced, so nochange in the amount of resin 22 used in coating the printed wiringboard 46 occurs.

[0125] A description will now be given of a resin coating methodaccording to a fourth embodiment of the present invention.

[0126]FIGS. 10A and 10B are diagrams of a resin coating apparatus usedto perform a resin coating method according to the fourth embodiment ofthe present invention, in which FIG. 10A shows a state prior to coatingand FIG. 10B shows a state at time of coating.

[0127] The resin coating apparatus 100 used to perform the resin coatingmethod according to the fourth embodiment is essentially the same as theresin coating apparatus 10 used to perform the resin coating methodaccording to the first embodiment as described above, with the additionhowever of a camera 58, a monitor 60 and a calculator 62. As shown inthe diagrams, the camera 58 is positioned at the tip of the nozzle 16 bfrom which the resin 22 is extruded.

[0128] A description will now be given of the resin coating methodaccording to the fourth embodiment of the present invention, using theresin coating apparatus 100 described above, with reference to FIGS. 10Aand 10B as well as FIG. 11.

[0129]FIG. 11 is a flow chart showing steps in a resin coating methodaccording to the fourth embodiment of the present invention.

[0130] Before the nozzle 16 b is lowered to a resin coating height H2 ata predetermined distance between the nozzle 16 b and the printed wiringboard 46, the resin 22 is extruded from the nozzle 16 b at an arbitraryheight H1 (FIG. 10A). At this time the extruded resin 22 formssubstantially a ball shape, with a top part of the ball attached to thetip of the nozzle 16 b in a step S400.

[0131] The ball of resin 22 is then photographed by the camera 58 and,through image analysis, a diameter D of the ball of resin 22 is obtainedin a step S402 by calculator 62.

[0132] A control signal 101 transmitted from the calculator 62 to thecontroller 14 based on the diameter data D obtained in the step S402,causing the syringe 16 to be lowered to the predetermined resin coatingheight H2 in a step S404, a height that corresponds to the diameter D. Abottom part of the resin 22 then contacts the printed wiring board,after which the syringe 16 is then raised, causing the resin 22 toseparate from the nozzle 16 b and spread across the printed wiring board46, coating same, in a step S406 (FIG. 10B).

[0133] At this time, an upper limit of the predetermined resin coatingheight H2 is set by the requirement that the bottom part of the ball ofresin 22 securely contact the printed wiring board 46 and, at the sametime, that the ball of resin 22 definitely separate from the nozzle 16 bwhen the syringe 16 is raised after the ball of resin 22 contacts theprinted wiring board 46. On the other hand, a lower limit of thepredetermined resin coating height H2 is set by the requirement that theresin not envelope the periphery of the nozzle 16 b and become attachedthereto when the resin 22 is held between the nozzle 16 b and theprinted wiring board 46. Accordingly, the desired height is determinedas appropriate by experiment.

[0134] With the conventional resin coating method, when for any reasonthe distance between the tip of the nozzle and the printed wiring boardto be coated is too short, the resin tends to stick to the tip of thenozzle after coating. If such a condition is allowed to continue throughsubsequent coating operations, then the amount of resin attached to thetip of the nozzle continues to accrete until suddenly dropping from thenozzle onto the printed wiring board, creating an abnormal coatingthereon.

[0135] By contrast, the resin coating method according to the fourthembodiment of the present invention prevents the above-describedsituation from occurring by setting the distance between the tip of thenozzle 16 b and the printed wiring board 46 to be, for example,substantially equal to the diameter D of the ball of resin 22 at the tipof the nozzle 16 b, thus preventing build-up of the resin 22 at thenozzle 16 b.

[0136] A description will now be given of a resin coating methodaccording to a fifth embodiment of the present invention.

[0137]FIG. 12 is a schematic diagram of a resin coating apparatus usedto perform a resin coating method according to a fifth embodiment of thepresent invention.

[0138] As shown in the diagram, the resin coating apparatus 110 used toperform the resin coating method according to the fifth embodiment ofthe present invention is essentially the same as the resin coatingapparatus 10 used to perform the resin coating method according to thefirst embodiment as described above, with the addition however of acamera 58, a monitor 60 and, further, a control device 112 and a washingunit.

[0139] As shown in the diagram, the camera 58 is positioned at the tipof the nozzle 16 b of the syringe 16 from which the resin 22 isextruded. The control device 112 measures the amount of residual resinattached to end 16 b of the nozzle 16 through image analysis, comparesthe measured amount to a predetermined value, and transmits a signal tothe washing unit to wash the nozzle end 16 b if the measured amountexceeds the predetermined value. The washing unit is equipped with awashing nozzle 114 that sprays the nozzle end 16 b with washing fluid.

[0140] A description will now be given of the resin coating methodaccording to the fifth embodiment of the present invention, using theresin coating apparatus 110 described above, with reference to FIG. 12and FIG. 13.

[0141]FIG. 13 is a flow chart showing steps in a resin coating methodaccording to the fifth embodiment of the present invention.

[0142] In a step S500 the camera 58 is positioned so as to observe theexternal appearance of the nozzle 16 b of the syringe 16.

[0143] The amount of resin 22 remaining on the periphery of the end 16 bof the nozzle 16 is quantified by the monitor 60 and the control device112 in a step S502.

[0144] The control device 112 determines whether the amount of resin 22attached to the nozzle 16 b exceeds a predetermined value S504 and, ifnot, continues surveillance of the nozzle 16 b by the camera 58. If,however, the amount of resin adhering to the nozzle exceeds thepredetermined value, then the control device 112 transmits a wash signal113 to the washing unit, so that the washing nozzle 114 sprays thenozzle end 16 b with washing fluid to remove resin 22 attached to thenozzle 16 b.

[0145] The above description is provided in order to enable any personskilled in the art to make and use the invention and sets forth the bestmode contemplated by the inventors of carrying out the invention.

[0146] The present invention is not limited to the specificallydisclosed embodiments, and variations and modifications may be madewithout departing from the scope and spirit of the present invention.

[0147] The present application is based on Japanese Priority ApplicationNo. 2000-293013, filed on Sep. 26, 2000, the contents of which arehereby incorporated by reference.

What is claimed is:
 1. A resin coating method for applying resin to apredetermined region of a printed wiring board comprising the steps of:imaging an external appearance of the resin extruded from a resinapplication device; and automatically adjusting an amount of the resinextruded from the resin application device based on the externalappearance of the resin obtained in the imaging step.
 2. The resincoating method as claimed in claim 1, further comprising the steps of:stretching the resin atop a stage prior to the imaging step; andmeasuring a surface area of the resin developed atop the stage after theimaging step using an image analyzer.
 3. The resin coating method asclaimed in claim 1, wherein the imaging step comprises exposing theresin to light of a predetermined wavelength so as to fluoresce theresin and separating fluorescent light so generated from light of otherwavelengths to obtain a fluorescent image of the resin.
 4. A resincoating method for applying resin to a predetermined region of a printedwiring board comprising the steps of: measuring a temperature of anextrusion nozzle of a resin application device; and automaticallyadjusting an amount of the resin extruded from the resin applicationdevice based on the temperature of the nozzle.
 5. A resin coating methodfor applying a resin to a predetermined region of a printed wiring boardcomprising positioning an extrusion nozzle of a resin application deviceat a predetermined reference height.
 6. A resin coating method forapplying resin to a predetermined region of a printed wiring board,comprising the steps of: imaging an external appearance of a resin dropafter the resin drop has been extruded from a nozzle of a resinapplication device but before the resin drop contacts the printed wiringboard; and adjusting a distance between a tip of the nozzle and theprinted wiring board based on the external appearance of the resin dropobtained in the imaging step.
 7. A resin coating method for applyingresin to a predetermined region of a printed wiring board, comprisingthe steps of: imaging a residual amount of the resin on an extrusionnozzle of a resin application device from which the resin is expelled;and washing the nozzle when the residual amount exceeds a predeterminedamount.
 8. A resin coating apparatus for applying resin to apredetermined region of a printed wiring board, comprising: an imagingunit for imaging an external appearance of the resin extruded from theresin coating apparatus; and an automatic adjustment unit forautomatically adjusting an amount of the resin extruded from the resincoating apparatus based on the external appearance of the resin obtainedin the imaging step.
 9. A resin coating apparatus for applying resin toa predetermined region of a printed wiring board, comprising: atemperature sensor for measuring a temperature of an extrusion nozzle ofthe resin coating apparatus; and an automatic adjustment unit foradjusting an amount of the resin extruded from the resin coatingapparatus based on the temperature of the nozzle.
 10. A resin coatingapparatus for applying a resin to a predetermined region of a printedwiring board, comprising: a positioning unit for positioning a tip of anextrusion nozzle of the resin coating apparatus at a predeterminedreference height.
 11. A resin coating apparatus for applying resin to apredetermined region of a printed wiring board, comprising: an imagingunit for imaging an external appearance of a resin drop after the resindrop has been expelled from an extrusion nozzle of the resin coatingapparatus but before the resin drop contacts the printed wiring board;and an adjustment unit for adjusting a distance between a tip of theextrusion nozzle and the printed wiring board based on the externalappearance of the resin drop.
 12. A resin coating apparatus for applyingresin to a predetermined region of a printed wiring board, comprising:an imaging unit for imaging a residual amount of the resin on anextrusion nozzle of the resin coating apparatus; and a washing unit forwashing the nozzle when the residual amount exceeds a predeterminedamount.